Re: Placeholder Variable (was: Perl 6 Debugging)

[Tom Browder]

On Sun, Mar 15, 2015 at 2:55 PM, Timo Paulssen  wrote:
...

Thanks, Timo!  Subroutine arg handling is an awkward but very exciting
improvement for an old but non-expert Perl 5 user.

Very briefly, how does one properly translate this to Perl 6:

sub foo {my @a = @_; }

Best,

-Tom

Re: Placeholder Variable (was: Perl 6 Debugging)

[Timo Paulssen]

On 03/15/2015 08:48 PM, Tom Browder wrote:
> The initial part of the code for the offending method definition is:
>
> method set_custom_ellipsoid
> {
> my ($name, $major, $recip) = @_;
> $name = uc $name;
> $recip = 0 unless defined $recip;
> if ($major) {
> %ellipsoids{$name} = [ $major, $recip ];
> } else {
> croak("set_custom_ellipsoid called without semi-major radius parameter");
> }
> set_ellipsoid($name);
> }
>
> I don't see the problem there.  Is it possible the problem is in one
> of the calls to the method?  I looked at all the calls but don't see
> an obvious problem.
>
> Thanks.
>
> -Tom

You're using @_ here, which in Perl 6 is a variable that indicates a
placeholder signature will be used. Another example of variables that
introduce a placeholder signature in the sub that contain them are $_
and $^foobar variables, like in:

@foobar.sort({ $^a.chars < $^b.chars })

So all you'll have to do is give your set_custom_ellipsoid method a
proper signature with $name, $major and $recip in them - and you can
even give $recip a default value so that you can get rid of the $recip =
0 unless defined $recip line, too.

regards
  - Timo